Biomedical subjects

E E Barnard

Publications and source records attributed to E E Barnard.

At least 19 recordsLinked to original sources

PubMed1982

Observations on no-stop and repetitive air and oxynitrogen diving.

The historical origins of the respective air decompression schedules of the British and United States Navies are reviewed with particular reference to the repetitive diving rules. No-stop diving is also discussed. A series of single dive and repetitive dive trials of the Royal Navy Air Table is presented. U.S. Navy and Royal Naval Physiological Laboratory (RNPL) 1968 repetitive dive rules were also tested according to their respective tables on a selection of dives. Comparison of the two methods produce a remarkably similar outcome for dives to similar depths. For dives to very dissimilar depths there is no comparison. The RNPL system has commendable simplicity but lacks the flexibility of the U.S. Navy system for use with successive dives to different depths. Observations on the results of a triple no-stop repetitive dive experiment are presented. It is concluded that little would be gained by further practical investigation of no-stop diving times.

Air↗

PubMed1981

Distribution of xenon gas exchange rates in dogs.

The kinetics of xenon gas uptake and elimination in seven anesthetized dogs were studied by simultaneous external recording of gas concentrations in several thousand anatomic sites during 7-h experiments. The data were analyzed by a previously described method of extracting moments of the distribution of gas residence times. Mean residence times (first moment) varied by more than a factor of 50 within a single animal: the fastest exchange was in the lungs (under 2 min), and progressively slower exchange occurred in the brain, spinal cord, ears, peripheral joints, and shoulder (over 2 h). Variance of the residence time (second moment) was found to approximate four times the mean residence time squared. This ratio was nearly the same throughout the body. Indications of unexpectedly high xenon solubility in the ear and joint regions were also found.

Animals↗

PubMed1981

Blood cell changes in asymptomatic divers.

Many recent reports have suggested that diving and decompression cause changes in blood cells even when no overt symptoms of decompression sickness are present. This study subjected 10 normal persons to a pressure exposure of 100 fsw (30.5 msw) for 60 min followed by the standard U.S. Navy decompression schedule. No subject had symptoms of clinical decompression sickness. Repeated blood samples over a 3-week period spanning the simulated dive were analyzed for numbers of red cells, white cells, reticulocytes, platelets (by three methods), and size distribution of platelets. The study was designed to detect postdive changes of less than 5%. Small but definite decreases were found in levels of red cells, white cells, hematocrit, and platelets (by microscopic methods but not by machine), and the proportion of large platelets rose. The changes were too mild to support a proposed mechanism of decompression damage.

Blood Cell Count↗

PubMed1980

Physiological aspects of naval problems.

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Aerospace Medicine↗

PubMed1979

Stochastic description of inert gas exchange.

Data from experiments measuring the rate of uptake and elimination of nonmetabolic gas in living organs are usually analyzed by several exponential time constants or their equivalent half-times (i.e, exponential series analysis). To avoid the limitations of this technique, we have formulated a method that combines analysis by moments of distribution with transfer function techniques, which makes the analysis independent of any mechanistic model. This method is an improvement over previous methods because it allows better comparison of gas exchange experiments and better prediction of gas exchange in the formulation of diver decompression schedules. Measurements of radioxenon uptake and elimination in two areas of a dog are presented. Analysis of the same organ response by both methods showed a fivefold variation in derived exponential time constants compared with less than 10% variation among moment descriptors.

Animals↗

PubMed1978

Nitrogen elimination during steady-state hyperbaric exposures.

Nitrogen elimination was measured in six divers during steady-state exposures in an oxygen-nitrogen atmosphere at 1, 2, and 3 ATA using both oxy-helium and pure O2 as washout gases. This was accomplished by using mass spectrometry to measure the expired N2 concentration breath-by-breath over periods of 120 min in all experimental conditions except for O2 breathing at 3 ATA, which was limited to 30-min periods. In all cases the area under the elimination curve increased with pressure. Total area under the curve was also greater when breathing O2 than when breathing oxy-helium, but this difference decreased with depth and washout time. Nitrogen elimination on a semilogarithmic plot falls rapidly during the first four minutes and then shows a slow linear fall for the remainder of the measurement period. Effective elimination of nitrogen decreased with depth and oxygen was more effective than oxy-helium in washing out nitrogen at all depths studied. Possible causes of the different variations noted in the washout curves during the experiment are discussed.

Atmospheric Pressure↗

PubMed1976